Corrosion inhibiting compositions

ABSTRACT

GREASES THICKENED WITH CONVENTIONAL GREASE THICKENERS AND CONTAINING A CLOUDY-TYPE OVERBASED ALKALI METAL OR ALKALINE EARTH METAL SULFONATE OR CARBOXYLATE DISPERSANT AND A WATER-SOLUBLE CORROSION INHIBITING SALT. CORROSION INHIBITING CONCENTRATES ARE ALSO SET FORTH WHICH COMPRISES LUBRICATING OIL, CLOUDY-TYPE OVER-BASED DISPERSANTS, AND WATER-SOLUBLE CORROSION INHIBITING SALTS.

3,730,895 CORROSION INHIBITING COMPOSITIONS Manley Kjonaas, Hammond,Ind., assignor to Atlantic Richfield Company, New York, N.Y. No Drawing.Filed Oct. 21, 1970, Ser. No. 82,800 Int. Cl. C10m 5/22, 5/14 U.S. Cl.252-18 32 Claims ABSTRACT OF THE DISCLOSURE Greases thickened withconventional grease thickeners and containing a cloudy-type overbasedalkali metal or alkaline earth metal sulfonate or carboxylate dispersantand a water-soluble corrosion inhibiting salt.

Corrosion inhibiting concentrates are also set forth which compriselubricating oil, cloudy-type over-based dispersants, and water-solublecorrosion inhibiting salts.

This invention relates to grease compositions which have improvedcorrosion inhibiting properties. More particularly, it relates togreases which include highly dispersed Water-soluble salts in amountseifective to inhibit corrosion.

Certain water-soluble salts have been recognized as efiicient corrosioninhibitors for lubricants. A problem encountered with these compositionshas been the inability to disperse the salt in sufliciently fineparticles throughout the lubricant. Greases which contain large solidparticles can harm the mechanical systems to which they are added.Federal Standard 291-3005 (Dirt Count Test) requires that a lubricant becompletely free of solid particles greater than 125 microns in size.Prior art compositions, however, contained much of the corrosioninhibitor as large particles so that although the grease was etfectivelycorrosion inhibited, the large particles caused the composition to beabrasive while in use. To be completely acceptable, greases shouldcontain very few solid particles over 25 microns in size, with the greatmajority of the particles being less than 5 microns.

Many dispersants have been used in attempting to reduce the size ofsolid particles in greases. Included among the dispersants that havebeen used are: water gelling agents (U.S. Pat. 3,098,849); the reactionproduct of an imidazoline and a fatty acid (U.S. Pat. 3,291,494); andcalcium mahogany sulfonates (U.S. Pat. 2,820,009). However, none ofthese dispersants are able to produce a completely acceptable solidparticle size range in lubricants. U.S. 'Pat. 2,820,009 teaches the useof calcium mahogany sulfonates to disperse an aqueous solution ofwater-soluble corrosion inhibitor in grease. However, since waterevaporates at elevated temperatures or under vacuum, the presence ofwater in the final grease product (as in the compositions of U.S. Pat.2,820,009) tends to limit the utility of the composition. When thegrease compositions of U.S. Pat. 2,820,009 are dehydrated, unacceptablylarge crystalline corrosion inhibitor particles may form. The problempresented is to provide a grease composition which is efiectivelycorrosion inhibited and contains solid corrosion inhibitor particles ofa completely acceptable size.

Therefore, one major object of the present invention is to provide agrease composition with improved corrosion properties. Other objects andadvantages of the invention will become apparent hereinafter.

It has now been discovered that a grease composition comprisinglubricating oil thickened to grease consistency, at least one cloudytype overbased alkali or alkaline earth metal dispersant and a corrosioninhibiting amount of water-soluble salt is corrosion inhibited andsubstantially all the solid particles of the water-soluble corrosioninhibitor contained in this grease composition are less than UnitedStates Patent 0 W 3,730,895 Patented May 1, 1973 about 5 microns insize. One embodiment of the present invention is a grease compositioncomprising: (1) a major amount of a lubricating oil thickened to greaseconsistency; (2) at least one cloudy type overbased alkali and/oralkaline earth metal dispersant in an amount from about 0.01 to about15%, preferably from about 0.01% to about 5%, by weight of the totalcomposition; and (3) at least one water-soluble salt in a corrosioninhibiting amount. It is preferred that the water-soluble corrosioninhibitor be present in the grease composition in an amount from about0.1% to about 5.0%, most preferably between about 0.1% and about 2.0%,by weight of the total composition. The grease composition of thepresent invention has corrosion inhibiting properties withoutdetrimentally affecting any of the lubricating qualities of the greasecomposition. It is, of course, understood that more than one overbaseddispersant and/or corrosion inhibitor can be used in combination in asingle grease and such a grease composition is within the scope of thepresent invention. The proportions given apply to the total amounts ofdispersants and/or water-soluble corrosion inhibitors regardless of howmany of each are used.

In a further embodiment, the present invention involes a composition ofmatter comprising: (1) a lubricating oil in an amount from about 30% toabout by weight of the total composition; (2) at least one cloudy typeoverbased alkali and/or alkaline earth metal dispersant in an amountfrom about 0.5% to about 30%, preferably from about 0.5 to about 20% byweight of the total composition; and (3) at least one water-soluble saltpresent in an amount such that when the total composition is added to agrease, the resulting grease will have a corrosion inhibiting amount ofsaid water-soluble salt, such amount of water-soluble salt being withinthe range of from about 0.5% to about 65%, preferably about 20% to about65%, by weight of the total composition. This embodiment of theinvention can be used as a corrosion inhibitor concentrate which can beadded to a base grease composition to produce a corrosion inhibitedgrease. The manufacture of a corrosion inhibitor concentrate, such asnoted above, permits a grease composition to be corrosion inhibited andreceive the other benefits of the invention with a minimum ofinconvenience and disruption of standard grease production. This is so,because the concentrate can be produced entirely independent of the basegrease composition (which is made in the conventional manner). Theconcentrate and base composition are then simply blended together in thedesired proportion. The concentrates in which the water-soluble salt isbetween about 20% and about 65% by weight of the total composition arepreferred since only small amounts of these concentrates need be addedto the base grease in order to render the product grease corrosioninhibited. This feature in turn adds to the convenience of using theconcentrates.

The oils used in the compositions of the present invention are thoseconventionally used in grease manufacture. These lubricating oilsinclude those having viscosity Within the range of about 50 SUS to about2000 SUS at F. These oils may be refined or otherwise processed toproduce an oil having the desired quality. Although mineral oils arepreferred, the oil may be synthetic in nature. Typical of the oils usedin the present invention is a mineral oil having a viscosity of about1100 SUS at 100 F. Combinations of two or more different oils in asingle grease composition are within the scope of the present invention.

The cloudy type overbased alkali and alkaline earth metal (i.e., sodium,potassium, lithium, magnesium, strontium, barium and calcium)dispersants useful in the present invention comprise: (1) alkali andalkaline earth metal salts of organic acids selected from the groupconsisting of sulfur acids, carboxylic acids, and mixtures thereof; and(2) solid particles of at least one oil-insoluble alkali and alkalineearth metal carbonates.

Specific examples of the metal salts of organic acids useful in thepresent invention are those derived from sulfur acids such as sulfonic,sulfamic, sulfinic and sulfenic acids. Of these, the salts derived fromsulfonic acids which include about 12 to about 200 carbon atoms are ofparticular usefulness in the present invention. Among the sulfonic acidsare the following: mahogany sulfonic acids, petrolatum sulfonic acids,monoand polywax substituted naphthalene sulfonic acids, phenol sulfonicacids, diphenyl ether sulfonic acids, diphenyl ether disulfonic acids,naphthalene disulfide sulfonic acids, naphthalene disulfide disulfonicacids, diphenyl amine disulfonic acids, cetyl-phenol mono-sulfidesulfonic acids, cetoxy caprylbenzene sulfonic acids, di-cetylthianthrene sulfonic acids, such as cetyl chloro-benzene sulfonic acids,cetyl-phenol sulfonic acids, cetyl-phenol disulfide sulfonic acids,cetyl-phenol mono-sulfide sulfonic acids, cetoxy capryl-benzene sulfonicacids, di-cetyl thiathrene sulfonic acids, di-lauryl beta-naphthaolsulfonic acids and di-capryl nitronaphthalene sulfonic acids, aliphaticsulfonic acids such as parafiin wax sulfonic acids, unsaturated paraffinwax sulfonic acids, hydroxy substituted paraffin wax sulfonic acids,tetraisobutylene sulfonic acids, tetra-amylene sulfonic acids,chloro-substituted paraffin wax sulfonic acids, nitroso paraffin waxsulfonic acids, etc., cycloaliphatic sulfonic acids, such as petroleumnaphthene sulfonic acids, cetyl-cyclopentyl sulfonic acids,lauryl-cyclohexyl sulfonic acids, bis-(diisobutyl)-cyclohexyl sulfonicacids, monoand poly-wax substituted cyclohexyl sulfonic acids, etc.

With respect to the sulfonic acids, it is intended herein to employ theterm petroleum sulfonic acids to cover all sulfonic acids which arederived at least in part from petroleum products. Additional examples ofsulfonic acids and/or the alkali and alkaline earth metal salts thereofwhich can be employed as starting mateirals are disclosed 508;2,193,824; 2,197,800; 2,202,791; 2,212,786; 2,213,- 360; 2,228,598;2,233,676; 2,239,974; 2,263,312; 2,276,090; 2,228,598; 2,233,676;2,239,974; 2,263,312; 2,276,090; 2,276,097; 2,315,514; 2,319,121;2,321,022; 2,333,568; 2,333,788; 2,335,259; 2,337,552; 2,346,568;2,366,027; 2,374,193 and 2,383,319.

Metal salts derived from carboxylic acids (i.e., carboxylates) are alsouseful in the present invention. The carboxylic acids include the fattyacids wherein there are present between about 12 to about 200-preferablyabout 12 to about 24 carbon atoms per molecule, such as, for example,palmitic, stearic, myristic, oleic, linoleic, etc. acids. The carboxylicacids of the aliphatic type can contain elements in the aliphaticradical other than carbon and hydrogen; examples of such acids are thecarbamic acids, ricinoleic acids, chloro-stearic acids, nitro-lauricacids, etc. In addition to the aliphatic carboxylic acids, it isintended to employ the cyclic types such as those containing a benzenoidstructure, i.e., benzene, naphthalene, etc., and an oil-solubilizingradical or radicals having a total of at least about 15 to 18 carbonatoms. Such acids are the oil-soluble aliphatic substituted aromaticacids as for example, stearyl-benzoic acids, monoor polywax substitutedbenzoic or naphthoic acids wherein the wax group contains at least about18 carbon atoms, cetyl hydroxy-benzoic acids, etc. The cyclic type ofcarboxylic acids also includes those which have present in the compounda cyclo-aliphatic group. Examples of such acids are petroleum naphthenicacids, cetyl cyclohexane carboxylic acids, di-lauryldeca-hydronaphthalene carboxylic acids, diooctyl cyclo-pentanecarboxylic acids, etc.

The present invention also includes compositions in which the highmolecular weight carboxylates, i.e., about C to about C preferably aboutC to about C are used in conjunction with low molecular weightcarboxylates have 1 to about 12 carbon atoms, preferably, about 2 toabout 4 carbon atoms per molecule. The more preferred high molecularweight carboxylates for use in the combination of carboxylate salts aremonoand dihydroxy aliphatic carboxylates, while the more preferred lowmolecular weight carboxylate is acetate. When this combination ofcarboxylate salts is used, it is preferred that the metal cation bealkaline earth, and in particular calcium. The mol ratio of lowmolecular weight carboxylate to high molecular weight carboxylate isbetween about 1 and about 15, preferably between about 3 and about 7.When a carboxylate is used in the practice of the present invention, itis preferred to use the high molecular weight-low molecular weightcombination of carboxylates, overbased with solid particles ofoil-insoluble carbonate. This combination of overbased carboxylates notonly has been found to be an effective dispersant for the corrosioninhibitor, but can also be used as a grease thickener. Therefore, thecarboxylate combination can perform a dual function in the greasecompositions of the present invention. The carboxylate combination can,however, function solely as a dispersant for water-soluble salts, suchas when used to produce corrosion inhibitor concentrates.

The overbased dispersants useful in the present invention are normallyprepared and maintained in an oil or other solvent carrier. However, thecomposition proportions given previously are on a solvent-free basis.Because of their availability and effectiveness as a dispersant in thecompositions of the present invention, the preferred dispersants are thecloudy type calcium sulfonates overbased with calcium carbonate.

Calcium sulfonates overbased with calcium carbonate can be obtained bypassing carbon dioxide through a mixture of neutral calcium sulfonates,mineral oil, lime and water. The formation of the overbased sulfonatescan be aided through the use of promoters, such as phenols, aromaticamines, sucrose and lower aliphatic alcohols. Many patents have beenissued which disclose processes for making calcium carbonate overbasedsulfonates. Among these are US. Pats. 2,865,956 and 2,956,018. The otherdispersants useful in the present invention can be prepared by methodsanalogous to that given above for the overbased calcium sulfonates.

It is essential to the success of the present invention that theoverbased dispersant used be of the cloudy type, i.e., the dispersantshould include particles, the major portion of which have a maximumdimension greater than about 60 A., and preferably greater than aboutA., in size, when the dispersant is in an oil carrier. It is preferredto limit the maximum dimension so that the dispersant particles in thefinal grease product are no larger than about 30,000 A. 3 (microns).With certain of the overbased dispersants, in particular thecarboxylates, the entire dispersant (and not just the carbonate) is oilinsoluble. These dispersants should have the particle sizes notedherein. The preferred dispersant, i.e. calcium sulfonate overbased withcalcium carbonate, may be termed a cloudy type overbased calciumsulfonate. This is so because when the mixture of oil-soluble sulfonateand oilinsoluble carbonate is suspended in mineral oil, the resultingsuspension appears cloudy, rather than clear to the naked eye. Thiscloudiness is a function of the particle size of the oil-insolublecarbonate. As the particle size of the insoluble salt increases, the oilsuspension undergoes a gradual change from clarity to cloudiness. Inorder to obtain a cloudy type overbased calcium sulfonate, a major partof the calcium carbonate particle present must be of a size such thatthe maximum dimension of the particle 1s at least 60 A., and preferablyat least 100 A., when the dispersant is in an oil carrier. (The termmaximum dimension as used herein refers to the largest straight linedimension of the particle, be it length, width, diameter or thickness.The term does not refer to the circumference of a spherical orcylindrical shaped particle.) Of course, the calcium carbonate particlesshould not be So large as to interfere with the quality of greases intowhich they are to be incorporated. This maximum size restriction variesfrom system to system and will depend on the quality of grease desired.For example, there may be certain situations where overbased calciumsulfonates in an oil carrier with major portions of the calciumcarbonate particles having maximum dimension greater than about 10,000A. (1.0 micron) would be disadvantageous. The preferred cloudy typeoverbased calcium sulfonates have a major part of the calcium carbonateparticles in the range of from about 300 A. to about 1200 A. (in an oilcarrier). Specific examples of the cloudy type calcium sulfonatespreferred for use in the present invention are products which include amajor portion of the calcium carbonate particles with a maximumdimension in the range of about 700 A. to about 900 A. (in an oilcarrier).

The Water-soluble corrosion inhibitors useful in the present inventionare well known to the art. Included among these corrosion inhibitors arealkali metal and am monium nitrites, carbonates, bicarbonates,sulphites, borates, chlorates, perchlorates, hypochlorites, silicates,phosphates, salicylates, citrates, tarnates, lactates, tartrates,oxylates, phthalates, acetates, iodates, arsenites, chromates,molybdates and tungstates, and amine nitrites, phosphates, and iodates.Because of their inexpensive cost and superior corrosion inhibitionproperties, the alkali metal nitrites and chromates, and mixturesthereof and in particular sodium nitrite, are preferred.

The materials used to thicken the grease compositions of the presentinvention to grease consistency are conven tional and well known in theart. Illustrative of these grease thickeners are alkali metal (e.g.,lithium and sodium) and alkaline earth metal (e.g., calcium, magnesium,strontium, and barium) hydroxy fatty acid soaps. These thickenerscomprise the soaps of hydroxy fatty acids having about 12 to about 24carbon atoms per molecule. Other grease thickeners, such as soaps fromlow molecular Weight fatty acids, that are well known in the art, arealso applicable to the present novel compositions.

These thickeners are added in an amount effective to give the mineraloil composition a grease-like consistency. In the preferred embodimentof the present invention, these thickeners comprise about 5% to about25% of the final grease product.

Additional components, such as oxidation inhibitors, detergents andother grease additives well known in the art, may be added to the greasecompositions of the present invention.

The following is one method by which the corrosion inhibitorconcentrates of the present invention may be produced. The base oil andoverbased dispersant are mixed together at a somewhat elevatedtemperature (130 F. to 200 F.) so that the viscosity of the mixture issufficiently low to allow efiicient blending. After the oil anddispersant are mixed, an aqueous solution of the corrosion inhibitingsalt(s) is added and the resulting combination, while being mechanicallyor otherwise stirred, is heated to about 300-350 F. under sufiicientpressure to prevent escape of the water and maintained at theseconditions for a period of time (about one hour) to allow the corrosioninhibitor to become completely dispersed. While maintaining an elevatedtemperature, the pressure is slowly vented and the corrosion inhibitorconcentrate is exposed to the atmosphere. This treatment substantiallydehydrates the product, leaving the concentrate substantially water-free(substantially dehydrating the concentrate means that the final greaseproduct partially derived from the concentrate can include less than0.1% by weight of water). It is an important advantage that theconcentrates and grease compositions of the present invention can besubstantially dehydrated without disturbing the dispersion of thecorrosion inhibitor. Greases which require the incorporation of water tomaintain the character of the grease cannot be used in instances, suchas high temperature or vacuum service, where the Water will evaporate orotherwise be removed from the grease composition. The greases of thepresent invention, which can be made water-free without destroying theimproved nature of the grease have no such disadvantage. Of course, itis not necessary that these grease compositions be anhydrous. After theconcentrate has cooled, the product optionally can be passed through anappropriately sized sieve or filter to remove trace amounts of largeparticles which may have formed. Except for these trace amounts, thecorrosion inhibitor exists in the concentrate as solid particles lessthan 5 microns (and normally less than about 3 microns) in size.

The concentrate, once prepared, may be blended with additional oiland/or grease thickening agent and other conventional grease additivesto give a grease composition according to the present invention. Theresulting grease composition is eifectively corrosion inhibited and lessthan 1% of the included solid corrosion inhibitor particles are greaterthan 5 microns in size (normally less than 1% of the included particlesare greater than about 3 microns in size).

The invention having been described in detail, the following examplesare provided to show specific embodiments of the compositions thereof.It will be understood the examples are given for illustration purposesonly and not by way of limitation.

EXAMPLE 1 This example illustrates the preparation of a finely dispersedsodium nitrite concentrate composition of the present invention. Thedispersant used was a cloudy type of overbased calcium sulfonate mixedwith an oil carrier. The overbased sulfonate (including the carbonate)comprised about 40% by weight of the total mixture. The sulfonate wasprepared from petroleum sources and contained about 20 to 40 carbonatoms per molecule and on the average, about 26 carbon atoms permolecule. The sulfonate-oil mixture had a base number of about 180. Themajor portion of the suspended calcium carbonate in this dispersant isin the form of platelets (i.e., cylinders) having a diameter within therange of about 700 A. to about 900 A. and a thickness in the range ofabout 70 A. to about A.

The concentrate was prepared as follows. 7.20 pounds of mineral oil(1100 SUS viscosity at F.) and 1.80 pounds of dispersant were charged toa pressure vessel equipped with a high speed mechanical mixer. Themixing motor was started and the temperature was increased to F. by useof electric heaters. 3.00 pounds of sodium nitrite disolved in 2.00pounds of hot water was added to the vessel. The vessel was then sealedand the temperature was increased to 337 F. The ingredients arethoroughly blended by the mechanical mixer. The pressure, which hadbuilt to 49 p.s.i.g. during heating and mixing was slowly vented to 5p.s.i.g. while the temperature was maintained at 329-337 F. The vesselwas repressured to 50 p.s.i.g. with air and the product was dischargedinto an open grease kettle preheated to 340 F. This step caused thewater to be driven off as steam and in effect dehydrated the product,i.e., the product was substantially water-free (the grease compositionmade from this concentrate had less than 0.1% by weight of water). Asample of the dehydrated product was examined under an opticalmicroscope with cross polarized illumination. The largest particleobserved was 3 microns. The major portion of the particles were in the 1to 3 micron range. The dehydrated product, or concentrate, was lightbrown in color and of a creamy consistency.

EXAMPLE 2 This example illustrates the production of a product having ahigher concentration of sodium nitrite than the product of Example 1.Except for the concentration differences, the procedure followed was thesame as in EX- ample 1. The following table gives the composition of thedehydrated products of Examples 1 and 2.

The dehydrated product of Example 2 was fluid. Under the opticalmicroscope, the largest observed particle was 150 microns in traceamounts (less than about 1% of the total sodium nitrite). Thisdehydrated product was passed through a 200 mesh sieve to give a finalconcentrate with the largest observed particle being 80 microns. Exceptfor trace amounts of particles (less than about 1% of the total sodiumnitrite) in the to 70 micron range, all the solid corrosion inhibitor inthe fluid concentrate was less than 5 microns in size. The concentratesof Examples 1 and 2 were stable dispersions in that only a trace of oilseparation was observed after storage for one month at room temperature.

EXAMPLE 3 In order to show the outstanding properties of the compositionof this invention using an overbased dispersant in which the majorportion of the solid particles have a maximum dimension greater thanabout 60 A. when in an oil carrier, a concentrate was prepared in amanner similar to that in Example 1, except that a clear type overbasedcalcium sulfonate was used as a dispersant. The clear sulfonate was acommercially available overbased calcium sulfonate (with about 300 totalbase number) in an oil carrier in which substantially all the solidparticles had a maximum dimension of less than 60 A. The composition ofthe dehydrated product was:

Percent by weight Sodium nitrite 30 Commercially available clearoverbased calcium sulfonate in oil carrier 15 Mineral oil 55 The sodiumnitrite in this product was in the form of coarse grains of sodiumnitrite (particle size about 50 to 150 microns). These particlesseparated from the oil after standing overnight.

EXAMPLE 4 The sodium nitrite concentrates of Examples 1, 2 and 3 wereincorporated into a standard lithium soap based grease (containing nocorrosion inhibitors) and the resulting greases were tested according tothe Dirt Count Test (FED-STD7913005). In brief, the Dirt Count Testinvolves observation of a portion of the composition under an opticalmicroscope to determine the size range of the solid particles in thecomposition. The greases made from the compositions of this invention(Examples 1 and 2) passed the Dirt Count Test, whereas the greasederived from the clear type overbased sulfonate (Example 3) failed thetest, indicting that this grease contained solid particles greater than125 microns in size.

This series of tests indicate that the compositions of the presentinvention allow one to control the size of solid corrosion inhibitorparticles in grease compositions.

EXAMPLE 5 The grease compositions that were prepared in Example 3)failed the test, indicating that this grease contained 1 and 2 weretested for rust resistance. A sample of the lithium based grease, withno sodium nitrite, was also 8 tested. The compositions of the variousgreases and test results are as follows:

These results show that not only is the sodium nitrite maintained withinan acceptable particle size range in the compositions of the presentinvention, but also the sodium nitrite contained therein is an elfectivecorrosion inhibitor at relatively low concentration.

EXAMPLE 6 This example shows the preparation of a concentratecomposition of this invention using a dispersant comprising acombination of carboxylates overbased with calcium carbonate. Thedispersant was prepared as follows:

A reaction vessel equipped with a high speed mixer was charged with 16.1lbs. of mineral oil having a viscosity of 1100 SUS at F. and 3.35 lbs.of hydrated lime. The mixer was activated and 1.79 lbs. of glacialacetic acid was added at a continuous rate over a 27 minute period oftime. The temperature was then increased to 176 F. by the use ofelectric heaters. 1.77 lbs. of the glyceride of 12-hydroxy stearic acidwas added and the reaction vessel was closed. The temperature was againraised to 292 F. Carbon dioxide was added so that the pressure increasedto 79 p.s.i. during a one-hour period. The temperature increased to 319F. during the carbonation period. The product was forced by pressureinto an open grease kettle which had been preheated to 340 F. After thisdispersant was cooled, an additional 2.0 lbs. of mineral oil and 0.1lbs. of oxidation inhibitor were added to give a composition which hadthe appearance of a grease. The composition had an ASTM worked 60 strokepenetration of 301 and an approximate total solids content of 26.8% byweight. All the solid particles had a maximum dimension of 3 microns orless with the major portion of these particles having a maximumdimension larger than 100 A.

A sodium nitrite concentrate (approximately 50% by weight) was made asfollows. A reaction vessel, equipped with a high speed mixer was chargedwith 1.05 lbs. of mineral oil and 2.45 lbs. of the previously madedispersant. The mixture was heated to F. and 3.5 lbs. of sodium nitritein 2.5 lbs. of hot water was added. The reaction vessel was closed andthe temperature was increased to 335 F. and the pressure increased to 48p.s.i. in a period of one hour. The gas was slowly vented over a periodof one hour while the temperature was maintained at 335 F. to 347 F. Theproduct was discharged to an open grease kettle and maintained for 1hour at 345 F. This treatment substantially dehydrated the product. Theproduct upon cooling had a fluid grease-like consistency and showed nooil separation on standing for 6 weeks at room temperature. Examinationunder an optical microscope showed that substantially all of the sodiumnitrite particles were under 3 microns in size with the largest particleobserved being 100 microns and present in trace amounts.

The concentrate was blended with a lithium soap based grease compositionin a proportion so that the final grease product had a sodium nitriteconcentration of 1.0% by weight.

EXAMPLE 7 This example shows that an effectively corrosion inhibitedgrease composition can be made directly from the combination of high andlow molecular weight carboxylates overbased with oil-insolublecarbonates without first preparing a corrosion inhibitor concentrate asin Example 6. The procedure followed was similar to that used in Example6 for the preparation of the overbased dispersant except thatimmediately after the addition of the glyceride of 12-hydroxy stearicacid, a 50% by weight aqueous solution of sodium nitrite was added in anamount such that the final grease composition contains 1% by weight ofsodium nitrite. All the calcium carbonate particles in this grease had amaximum dimension less than 3 microns in size with the major portionhaving a maximum dimension larger than 100 A. Substantially all thesodium nitrite particles were below 3 microns in size with only a traceamount as large as 100 microns.

The grease products of Examples 6 and 7 were tested for both corrosioninhibiting properties and particle size. The results of these tests areas follows:

Examples 1 to 5 show that the compositions of the present invention formstable dispersions which have excellent corrosion properties as well asbeing able to meet the Dirt Count Test. These examples also indicatethat grease compositions which do not include the cloudy type overbaseddispersants do not have the outstanding properties of the compositionsof the present invention.

Examples 6 and 7 indicate that a combination of both high and lowmolecular weight carboxylate overbased with oil insoluble carbonate canbe used solely as a dispersant for corrosion inhibitor or as both adispersant and grease thickener. In either case, the final greasecompositions is effectively corrosion inhibited with finely dispersedsolid particles of corrosion inhibitor.

The compositions of the present invention can be substantiallydehydrated without disrupting the stability of the dispersion. As hasbeen noted previously, this property is advantageous in greases whichare to be used in severe applications, for example, at high temperaturesand under vacuum.

While in the foregoing disclosure certain examples have been set forthwhich illustrate details specifying modes of applying this invention, itshould be understood that such details may be varied considerably by oneskilled in the art without departing from the spirit of this invention.

What is claimed is:

1. A grease composition comprising: (1) a major amount of a lubricatingoil thickened to grease consistency; (2) at least one cloudy typeoverbased alkaline earth metal dispersant and being present in an amountfrom about 0.01% to about 15% by weight of the total grease composition,said dispersant comprising (a) at least one salt of an organic acidselected from the group consisting of sulfonic acids, carboxylic acidsand mixtures thereof, and (b)' solid particles of at least oneoilinsoluble alkaline earth metal carbonate, said dispersant containingparticles, the major portion of which have a maximum dimension greaterthan about 60 A. when said dispersant is in an oil carrier; and 3) atleast one watersoluble salt in a corrosion inhibiting amount selectedfrom the group consisting of alkali metal nitrites, alkali metalchromates, and mixtures thereof and having a particle size less than 5microns.

2. The composition of claim 1, wherein said organic acid is a sulfonicacid having about 12 to about 200 carbon atoms per molecule.

3. The composition of claim 2, wherein said dispersant includesparticles the major portion of which have a maximum dimension greaterthan about 100 A. when said dispersant is in an oil carrier and lessthan about 3 microns when said dispersant is in said grease composi- 5.The composition of claim 4, wherein the major portion of the calciumcarbonate particles are within the range of from about 300 A. to about1200 A. in size when said dispersant is in an oil carrier.

6. The composition of claim 5, wherein the major portion of the calciumcarbonate particles are within the range of from about 700 A. to about900 A. in size when said dispersant is in an oil carrier.

7. The composition of claim 6, wherein said watersoluble salt is sodiumnitrite present in an amount from about 0.1% to 5.0% by weight of thetotal grease composition.

8. The composition of claim 7, wherein said composition is substantiallydehydrated.

9. The composition of claim 1, wherein said organic acid is a carboxylicacid having between about 12 and about 200 carbon atoms per molecule.

10. The composition of claim 1, wherein said cloudy type overbaseddispersant comprises (1) at least one high molecular weight carboxylatehaving between about 12 to about 200 carbon atoms per molecule and a lowmolecular weight carboxylate having between 1 to about 12 carbon atomsper molecule.

11. The composition of claim 10, wherein said cloudy type overbaseddispersant comprises 1) at least one high molecular weight carboxylatehaving between about 12 to about 24 carbon atoms per molecule and atleast one low molecular weight carboxylate having between about 2 toabout 4 carbon atoms per molecule, wherein the ratio of said lowmolecular weight carboxylate to said high molecular weight carboxylateis between about 1 to about 15, said dispersant including particles themajor portion of which have a maximum dimension greater than about 100A. when said dispersant is in an oil carrier and less than about 3microns when said dispersant is in said grease composition.

12. The composition of claim 11, wherein the mol ratio of said lowmolecular weight carboxylate to said high molecular weight carboxylateis between about 3 and about 7, and said high molecular weightcarboxylate and low molecular weight carboxylate are calcium salts, saidoil-insoluble carbonate is calcium carbonate.

13. The composition of claim 11, wherein said high molecular weightcarboxylate is selected from the group consisting of monohydroxyaliphatic carboxylates and dihydroxy aliphatic carboxylates and said lowmolecular weight carboxylate is acetate.

14. The composition of claim 13, wherein said watersoluble salt issodium nitrite.

15. The composition of claim 14, wherein said composition issubstantially dehydrated.

16. A composition of matter for use as a corrosion inhibitor concentratein the preparation of a grease composition comprising: (l) a lubricatingoil in an amount from about 30% to about by weight of the totalcomposition; (2) at least one cloudy type overbased alkaline earth metaldispersant, said dispersant being present in an amount from about 0.5%to about 30% by weight of the total composition, said dispersantcomprising (a) at least one salt of an organic acid selected from thegroup consisting of sulfonic acids, carboxylic acids and mixturesthereof, and (b) solid particles of at least one oil-insoluble alkalineearth metal carbonate, said dispersant containing particles the majorportion of which have a maximum dimension greater than about 60 A. whensaid dispersant is in an oil carrier; and (3) at least one Water-solublesalt selected from the group consisting of alkali metal nitrites, alkalimetal ch'romates, and mixtures thereof and having a particle size lessthan 5 microns and being present in an amount such that when the totalcomposition is added to said grease composition, said grease compositionwill have a corrosion inhibiting amount of said water-soluble salt, saidamount of water-soluble salt being within the range of about 0.5 toabout 65% by weight of the total composition.

17. The composition of claim 16, wherein said organic acid is a sulfonicacid having about 12 to about 200 carbon atoms per molecule.

18. The composition of claim 17, wherein said dispersant includesparticles the major portion of which have a maximum dimension greaterthan about 100 A. when said dispersant is in an oil carrier and lessthan about 3 microns when said dispersant is in said grease composition.

19. The composition of claim 18, wherein said amount of water-solublesalt is within the range of about to about 65% by weight of the totalcomposition.

20. The composition of claim 18, wherein said dispersant is calciumsulfonate overbased with calcium carbonate.

21. The composition of claim 20, wherein the major portion of thecalcium carbonate particles are within the range of from about 300 A. toabout 1200' A in size when said dispersant is in an oil carrier.

22. The composition of claim 20, wherein the major portion of thecalcium carbonate particles are within the range of from about 700 A. toabout 900 A. in size when said dispersant is in an oil carrier.

23. The composition of claim 22, wherein said watersoluble salt issodium nitrite.

24. The composition of claim 23, wherein said composition issubstantially dehydrated.

25. The composition of claim 16, wherein said organic acid is acarboxylic acid having between about 12 and about 200 carbon atoms permolecule.

26. The composition of claim 16, wherein said cloudy type overbaseddispersant comprises at least one high molecular weight carboxylatehaving between about 12 to about 200 carbon atoms per molecule and atleast one low molecular weight carboxylate having between 1 to about 12carbon atoms per molecule.

27. The composition of claim 26, wherein said cloudy type overbaseddispersant comprises at least one high molecular weight carboxylatehaving between about 12 to about 24 carbon atoms per molecule and atleast one low molecular weight carboxylate having between 2 to about 4carbon atoms per molecule, wherein the mol ratio of said low molecularweight carboxylate to high molecular weight carboxylate is between about1 to about 15, said dispersant including particles the major portion ofwhich have a maximum dimension greater than about A. when saiddispersant is in an oil carrier and less than about 3 microns when saiddispersant is in a grease composition.

28. The composition of claim 27, wherein the mol ratio of said lowmolecular weight carboxylate to said high molecular weight carboxylateis between about 3 to about 7.

29. The composition of claim 27, wherein said high molecular weightcarboxylate and said low molecular weight carboxylate are calcium saltsand said oil-insoluble carbonate is calcium carbonate.

30. The composition of claim 29, wherein said high molecular weightcarboxylate is selected from the group consisting of monohydroxyaliphatic carboxylates and dihydroxy aliphatic carboxylates and said lowmolecular weight carboxylate is acetate.

31. The composition of claim 30, wherein said watersoluble salt issodium nitrite.

32. The composition of claim 31, wherein said composition issubstantially dehydrated.

References Cited UNITED STATES PATENTS 2,820,009 1/1958 Smith et al.25218 3,065,176 11/1962 Blake et al. 252-18 2,956,018 1'0/1960 Carlyleet al. 252--18 FOREIGN PATENTS 778,468 7/1957 Great Britain 252-18PATRICK P. GARVIN, Primary Examiner I. VAUGHN, Assistant Examiner U.S.Cl. X.R. 252-17, 25, 389

